Gate driver On Array (GOA) is a technique for integrating a gate driver integrated circuit of a Liquid Crystal Display (LCD) onto an array substrate. A GOA circuit has a number of cascaded GOA units each constituting a shift register. For a GOA unit at a particular stage, its input signal is an output signal from a GOA unit at its previous stage and its output signal is a reset signal for the GOA unit at its previous stage. The output signals from the GOAs at the respective stages are at high level sequentially for scanning an LCD panel on a per-line basis.
Since an output signal from a GOA unit at a particular stage is an input signal to the GOA unit at its next stage, an abnormality in the output signal from the GOA unit at the particular stage will cause abnormalities in the output signals from the subsequent GOA units, resulting in a display abnormality of an LCD panel eventually. In order to determine the defective GOA unit, typically the GOA units at the respective stages are connected to an oscilloscope sequentially. It can be determined whether the GOA unit at each stage is defective based on whether the waveform of the output signal from the GOA unit as displayed on the oscilloscope is normal or not. Hence, it is problematic at least in that connecting the GOA units at the respective stages to the oscilloscope sequentially is troublesome and inefficient for detection.